Cycles render won't render one object
Right now your ground plane is set to a layer that has not been set to render.

Move the ground plane that remains black to a layer thats beïng rendered like Layer 1. (Select the plane, press M, and select the first box)



Or enable the layer which contains the ground plane in your scene settings. (shift + LMB on the box/layer which contains the ground plane)



Hope this works for you...

B.t.w. The smoke texture from the other plane is missing. You can pack this in your blendfile using File > External Data > Pack all into blendfile or auto pack.